Boundaries with a color might be resolved beyond the stair-case representation
offered by the mesh by creating a polynomial representation of the color
values within the intersected elements.
For this you need to define a subresolution table, describing at least the
polynomial degree that should be used for this information.
When this table is defined, you can indicate that a (colored) boundary is to
be subresolved by stating subresolution = true in its attribute.
Polynomial information will be created per color and is accessible as a property in the mesh afterwards.